A violent family

In 1993, Dutch scientists found a family in which several men seemed prone to unusually aggressive behaviour. They all had a variant of a gene that usually makes a protein responsible for breaking down chemicals in the brain. The affected men had abnormally high levels of these chemicals, which the researchers think may have caused their aggression. However, this gene variant has not yet been found in any other families and so it could just be a coincidence.

Members of a Dutch family, in which several men were unusually aggressive, all had a variant of a gene that usually makes a brain protein.